228
Spirometry • Occupational and Environmental Lung Disorder Committee
ACOEM POSITION STATEMENT
ACOEM Position Statement
Spirometry in the Occupational Setting
Lead Author:
Mary C. Townsend, DrPH
Improved quality and standardization of spirometry testing and interpretation of results are critically important in the occupational setting.
This position statement is meant to
contribute to that goal by increasing
the occupational medical community's awareness of the importance and
complexities of spirometry testing.
The position statement reviews: basic principles of spirometry and indications for spirometry in occupational medicine; essential criteria for
ensuring validity of spirometric results; and proper interpretation of
results, including selection and raceadjustment of predicted values, comparison with predicted values, assessment of loss of function over
time, response to a bronchodilator
and acute changes associated with
workplace exposures. The American
College of Occupational and Environmental Medicine (ACOEM)
makes detailed recommendations in
each of these areas, and key points
are summarized in tables throughout
this position statement.
Spirometry in the Occupational
Setting
This position statement provides
the occupational physician with
guidelines for using spirometry testing in workplace medical programs.
The focus is primarily on conducting
and interpreting spirometry tests in
individual workers, although spirometry data are also analyzed for groups
of workers in respiratory surveillance programs and epidemiologic
research studies. The topics reviewed
by this position statement are presented in Table 1. A glossary of
pulmonary function terms and abbreviations is provided in the Appendix.
Principles of Spirometry
Spirometry is the most basic and
frequently performed test of pulmonary function, measuring the ventilatory function of the respiratory system, ie, the ability to move air into
and out of the lungs. Using a forced
expiratory maneuver, which is a
maximal expiration from total lung
capacity to residual volume, spirometry measures volumes and flow
rates. The expired air is measured by
a spirometer, and the graphic recording of the expiration is called a spirogram. For the past 50 years, volume-time spirograms have displayed
expired volume as a function of expiratory time (Fig. 1). Since the mid1970s, flow-volume spirograms
have also become common, showing
expiratory flow rate as a function of
expired volume (Fig. 2). As described below, both displays are critical in assessing the technical quality
of a test. Because spirometry is based
on a maximal, forced expiratory maneuver, the accuracy of its results are
effort-dependent, requiring a subject's full understanding, cooperation, and effort.
Three clinically useful measurements are obtained from a properly
performed spirometry test. The
forced vital capacity (PVC) measures the total volume of air exhaled
during the maneuver. Speed of the
expiratory airflow is quantified by
the forced expiratory volume in one
second (FEV 1)' and by the relationship of the FEV 1 to the PVC, ex-
pressed as the FEV IIFVC ratio.
These measurements are usually
compared with average values "predicted" for a subject on the basis of
sex, age, height, and race. An FEV 1/
PVC that is below the lower limit of
a subject's normal range for this ratio
indicates probable airways obstruction. The severity of obstructive impairment is determined by the degree
of FEV 1 reduction relative to its
normal range. In the absence of airways obstruction, an PVC that is
below the lower limit of a subject's
normal range suggests restriction of
lung volume; the severity of restrictive impairment is reflected by the
degree of PVC reduction. In addition, changes in PVC and FEV 1 can
be measured over time to determine
whether loss of function is excessive.
However, the criteria for evaluating
longitudinal changes in individuals
are less standardized.
An additional measurement, the
forced expiratory volume in six seconds (FEV 6)' is currently under consideration as a surrogate for the PVC,
particularly in the screening setting.
However, at the present time, few
sets of predicted values include the
FEV6' limiting its usefulness. As
predicted values are published for
the FEV 6' it may become an easily
standardized substitute for the PVC
in assessing impaired pulmonary
function. It is important to note that
the FEV 6 must be compared with a
predicted FEV6 , not a predicted
PVc.
Indications for Spirometry in
Occupational Medicine
When used appropriately, spirometry can play an important role in the
primary, secondary, and tertiary pre-
229
JOEM • Volume 42, Number 3, March 2000
TABLE 1
Spirometry in the Occupational
Setting: ACOEM Position Statement
Topics
•
•
•
•
•
Principles of Spirometry
Indications for Spirometry in Occupational Medicine
Essential Components of Valid Spirometry
Equipment Performance
Testing Technique
Measurement of Results
Technician Training
Interpretation of Results
Selection of Reference Values
Race-Adjustment of Predicted Values
Cross-Sectional Evaluation: Normal,
Obstructed, Restricted
Changes Over Time
Pre- to Post-Bronchodilator Changes
in Pulmonary Function
Acute Work-Related Changes in Pulmonary Function
Summary
1
2
3
4
5
6
7
8
9
10
Time (seconds)
Fig. 1. Volume-time curve.
12
:;;
c
3CD
.!!!
e
~
~
o
u::
10
PEF
8
6
4
2
FVC
•
2
3
4
Volume (liters)
5
6
Fig. 2. Flow-volume curve.
vention of respiratory disease in the
workplace. 1
In the primary prevention of respiratory disease, spirometry can be
used in pre-placement and fitnessfor-duty examinations of individuals
when: (l) the physical demands of a
job require a certain level of cardiopulmonary fitness, eg, heavy manual
labor or firefighting; or (2) the characteristics of respirator use can impose a significant burden on the cardiopulmonary systems, eg, use of a
self-contained breathing apparatus,
or prolonged use of certain negativepressure masks under conditions of
heavy physical exertion and/or heat
stress,z·3 Although not required routinely under the Occupational Safety
and Health Administration (OSHA)
Respiratory Protection Standard, 29
CPR 1910.134, spirometry may be
used in the evaluation of respirator
users in some situations.v "
In addition to pre-placement
screening of individuals, primary
prevention of occupational respiratory disease also includes research
and monitoring of health status in
groups of workers. Potential health
effects are assessed in occupational
groups by comparing workers ex-
posed to an agent or process with
those not exposed and/or those with
varying levels of exposure. This aspect of primary prevention is particularly important in occupational
medicine to detect previously unrecognized health consequences of occupational exposures to specific
agents.
In the secondary prevention of respiratory disease, repeated spirometric evaluations can be used in medical surveillance programs when
workplace exposures put workers at
risk of developing occupationally related respiratory disorders. I Surveillance is needed to detect the slowly
developing or delayed losses of function that characterize many workrelated respiratory disorders. In this
case, many healthy individuals are
tested to detect early excessive declines in the pulmonary function of a
subgroup of sensitive workers, even
though the spirometry test results of
these workers may still remain in the
normal range.
Respiratory surveillance programs
require that a baseline be established
and that workers be re-tested periodically. These periodic spirometry
tests may be mandated by OSHA
regulations (eg, for employees exposed to asbestos, cadmium, coke
oven emissions, or cotton dust and
for respirator-wearers exposed to
benzene, formaldehyde, or methylene chloride) or recommended by
OSHA Special Emphasis Programs
(eg, Silicosis). The contents of the
OSHA-mandated physical examinations are summarized in a 1998 publication from the US Department of
Defense Occupational Medical Surveillance Manual? The National Institute for Occupational Safety and
Health (NIOSH) also recommends
respiratory surveillance for more
than 25 additional exposures that do
not have OSHA-mandated surveillance programs." Periodic spirometry
tests may also be part of industry- or
company-mandated medical surveillance programs or a component of
workplace health promotion programs. As will be discussed later in
this position statement, the limitations of spirometry must be borne in
mind when interpreting periodic spirometry test results in individuals.
Although spirometry can detect large
changes over a short time or smaller
changes cumulated over a longer observation period, it is not sensitive to
small, short-term changes in an individual's pulmonary function.
In the tertiary prevention of respiratory disease, spirometry is used in
the clinical evaluation of symptomatic individuals, because many pulmonary diseases manifest themselves as restrictive, obstructive, or
combined ventilatory defects. Spirometry allows some quantification
of the severity of lung function loss
and is one of the pulmonary function
tests used in assessing respiratory
impairment. Spirometry may be a
required component in the evaluation
of workers for disability under the
Social Security Administration," the
Federal Coal Mine Health and Safety
Act," and in the workers' compensation setting. 9 , l0 Although mild spirometric abnormalities are "usually not
correlated with diminished ability to
perform most jobs," "progressively
230
Spirometry • Occupational and Environmental Lung Disorder Committee
lower levels of lung function [are]
correlated with diminishing ability to
meet the physical demands of many
jobS."lO Additional measures of
functional impairment, such as determination of diffusing capacity for
carbon monoxide,11 measurement of
lung volumes.V exercise tolerance
testing.'? or methacholine challenge
testing.l" are beyond the scope of
this position statement.
Essential Components of Valid
Spirometry
Spirometry is simple but fraught
with technical pitfalls that can invalidate the pulmonary function measurements. Failure to obtain full understanding, cooperation, and effort
from a subject during any part of the
test usually results in an underestimation of the true pulmonary function. Poorly maintained spirometers
also affect the accuracy of observed
spirometric values. 1S-17 Such erroneous measurements may cause a normal, healthy subject to be mislabeled
as "impaired" or lead to incorrect
assessments of impaired subjects.
When evaluating changes over time,
small decrements in pulmonary function may be lost in the noise of the
measurements if testing equipment
and/or technique are not as accurate,
precise, rigorous, and standardized
as possible.l'' For analysis of group
data, small differences between
groups, which may be scientifically
important, can be obscured by poor
quality data caused by inadequate
testing technique.
In occupational medicine, the consequences of such misinterpretations
can go beyond simply making an
inaccurate diagnosis; decisions regarding fitness for duty, workplace
accommodation, and compensation
for work-related illness may also be
affected. Furthermore, because occupational spirometry tests are often
conducted in the regulatory and medical-legal arenas, the validity of the
spirometry test is likely to be scrutinized. Therefore, it is critical for
both clinical and administrative pur-
poses that occupational medicine
physicians understand the need for
standardization and quality control in
spirometry.
Although timed forced expirations
have been measured since the
1950s,19 it has only been in the past
2 decades that spirometry standardization and quality control have been
emphasized. The American Thoracic
Society (ATS) has been at the forefront of these efforts, with spirometry standardization statements and
updates issued in 1979,20 1987,21
and 1995,22 as well as interpretation
guidelines issued in 1991. 23 Recommendations for infection control and
hygiene during spirometry testing
are included in the most recent ATS
Spirometry Update,22 and current research supports the continued validity of these recommendations. 24-27
As listed in Table 1, validity of
spirometry tests is affected by four
elements: (1) equipment performance, (2) testing technique, (3)
measurement of results, and (4) technician training. Although the details
of each of these topics are extensively discussed in the 1994 ATS
Update 22 and in applicable regulations, 7.8,28 some key aspects that are
often not appreciated by the occupational health community are highlighted below.
Equipment Performance
As summarized in Table 2, spirometers can beclassified into one of
two types, depending on their mechanical characteristics: volumetric
spirometers accumulate and directly
measure exhaled air volume as a
function of time; flow-type spirometers indirectly measure airflow during exhalation and integrate the
flows to obtain expired volume. 19,29-33 Although volume and
flow-type spirometers are distinguished by their mechanical characteristics, it should be noted that both
types of spirometers can produce
both volume-time and flow-volume
spirograms if the spirometry software is programmed appropriately.
TABLE 2
Types of Spirometers
Volumetric spirometers:
• Accumulate and directly measure
exhaled air volume as a function of
time
• Examples are water-sealed, dry roIling seal, and bellows spirometers
• Provide direct volume-time tracing
• In general, are precise, simple to operate, and easy to maintain
• May be slightly unwieldy owing to
size and weight
Flow-type spirometers:
• Indirectly measure airflow during exhalation; integrate the flows to obtain
expired volume
• Examples are pneumotachometer,
turbine, hot wire anemometer spirometers
• Large range of flows are measured
during a forced expiration: flow sensors may perform better at high flow
rates (early in maneuver) than at low
flow rates (end of maneuver)
• Often more variable (less precise)
than volumetric spirometers
• Integrity of sensors must be maintained for accurate spirometry measurements-if sensor is damaged,
blocked, or has moisture condensation or obstruction by mucus, test
results may be erroneous
• Malfunctions in sensors, transducers,
and electronics can go unnoticedusers must be alert for anomalous
results
• Lightweight and portable
In general, volumetric and flowtype spirometers each have advantages and disadvantages. In a volumetric spirometer, the subject's
expired air may: (1) cause a collection bell to rise in a water jacket
(water-sealed spirometer); (2) displace a piston horizontally in a cylinder, causing the seal between the
piston and cylinder to roll on itself
(dry rolling seal spirometer); or (3)
fill a bellows (bellows spirometer).
The air-collecting part of the spirometer often has a direct pen linkage,
inscribing a volume-time spirogram
on moving chart paper during testing
of a subject. In general, volumetric
spirometers are precise, operate simply, and are easily maintained. The
chief disadvantage of volume spirometers is their size, because they
JOEM • Volume 42, Number 3, March 2000
231
TABLE 3
Equipment Performance Recommendations
1. For volumetric and flow-type spirometers, ATS recommends:
• Minimal performance criteria for range of volumes and flow rates, accuracy, precision, size of graphical display
• Validation by laboratory testing with known waveforms to determine whether specific spirometer models meet ATS performance criteria
• Frequent quality control (calibration) checks to ensure that spirometers remain accurate during use
2. An occupational spirometry testing system should meet as many of the following criteria as possible:
• Have the highest degree of accuracy and precision, exceeding ATS recommendations, particularly when serial spirometry measurements will be evaluated for small changes over time
• Provide real-time volume-time and flow-volume curves to technician for recognizing testing errors
• Provide extensive computer-derived technical quality indicators
• Save all test results and test quality indicators from a test session
• Save adequate data points to reconstruct tracings electronically at a future time
3. ACOEM recommends that users:
• Request written verification from the manufacturer that a particular spirometer has successfully passed its validation checks using
the 1994 ATS Update protocol
• Save electronic copies or hard copies of whole spirograms so that technical quality of past tests can be examined when necessary
• Be able to examine volume-time curves to check end of test and flow-volume curves to check start of exhalation to determine
whether test results are probably valid or reflect obvious testing artifacts
• Save calibration tracings and records to support validity of spirometry tests
• Maintain a log of problems found/solved and changes made in protocol, computer software, or equipment
4. Many NLHEP testing procedures and "office spirometers" are not acceptable for diagnostic spirometry or for occupational screening,
surveillance, and impairment evaluations.
must be able to accumulate 8 L of
expired air.
Flow-type spirometers, on the
other hand, are lightweight and portable because their components are
small, but their mechanical operating
characteristics are complex because
the measurement of expired volumes
is indirect and the range of flows to
be measured during a forced expiration is large.3 3 Different flow-type
spirometers measure: (l) pressure
differentials created as expired air
passes through an orifice or across a
resistance element, eg, composed of
parallel capillary tubes or a mesh
screen (pneumotachometer); (2) rotation speeds of a turbine as expired
air flows across it (turbine); or (3)
electrical current required to maintain the temperature of a heated wire
as expired air flows across it (hot
wire anemometer). The relationship
between the measured index (ie,
pressure, turbine speed, or electrical
current) and flow rate is not always
linear, and many flow sensors perform better at high flow rates, which
are encountered early in the forced
expiration, than they do at low flow
rates, which are seen at the end of the
maneuver, particularly in subjects
with airways obstruction. In general,
flow-type spirometers exhibit more
variability (less precision) than volumetric spirometers, which can adversely affect interpretation of the
serial spirometry measurements of
medical surveillance programs. 33
Because a flow-type spirometer
sensor is designed to detect pressure,
turbine speed, or electrical current,
and the transducer is calibrated to
relate the measured index to rates of
airflow, the integrity of the sensor
must be maintained to achieve accurate measurements of pulmonary
function. The characteristics of the
sensor may become modified during
spirometry tests if the sensor is damaged, blocked, or if moisture condenses on or mucus obstructs a resistance element, turbine, or hot wire.
Such altered sensor characteristics or
other electronic problems may produce test results that are erroneous,
eg, flow rates that exceed the maximum flow capability of the instrument, exhaled volumes that far exceed those expected for the subject,
or results that continually improve
during a test session for every subject tested. It is critical that users be
alert for such subtle indications of
malfunction.
Unlike respirators, spirometers are
not certified or approved by a government or private agency. However,
as shown in Table 3, for both types
of spirometers,the ATS recommends
minimal performance criteria (including size of graphical display),
validation of spirometers to determine whether specific models meet
the performance criteria, and frequent quality control (calibration)
checks to ensure that spirometers
remain accurate during use.22 The
requirements of the Social Security
Administration7 and the Federal
Coal Mine Health and Safety Act"
differ from the ATS recommendations in some details; these regulations should be consulted before conducting spirometry tests for
impairment/disability evaluations.
The 1994 ATS Update presents a
spirometer testing protocol for validating the accuracy and precision of
each spirometer mode1. 22 This testing can be performedby a spirometer
manufacturer or by an independent
testing laboratory. The validation
protocol uses standard waveforms"
to drive a mechanical syringe, deliv-
232
ering known volumes at known
speeds into the spirometer and software to be tested." The 1994 ATS
Update testing protocol is far more
rigorous than previous ATS recommendations, so users should be certain that their spirometer was tested
using the 1994 ATS protocol. The
ACOEM recommends that users request written verification from the
manufacturer indicating that a particular spirometer has successfully
passed its validation checks, and that
the tested spirometer and software
version correspond with the model
and software version that is being
purchased. However, it must be
stressed that such validation under
laboratory conditions does not guarantee that a device will retain its
accuracy and precision under field
conditions. The importance of frequent calibration checks in the field
cannot be overstated.
Even when spirometers meet the
minimal criteria set out by the ATS,
they still vary in the accuracy and
precision with which they measure
expired volumes of air, in the completeness of the visual display presented to the technician for recognizing testing errors, in the availability
of extensive computer-derived technical quality indicators,36-39 in the
information that is saved as a testing
session progresses and after the session is completed, and finally, in
whether data points from tracings are
saved so that the tracings can be
recalled at a later date for comparison with other tests or for quality
control reviews of spirograms (Table
3). The best systems far exceed ATS
recommendations for accuracy and
precision, provide real-time visual
displays of the expiratory maneuver
as well as computer-derived technical quality indicators, store all information from a test session, and save
data points so that tracings can be
reconstructed electronically at a future time. Users must remember that
the highest degree of precision and
accuracy is needed when serial spirometry measurements will be evaluated for small changes over time.
Spirometry • Occupational and Environmental Lung Disorder Committee
Unless the spirometry system
saves electronic copies that permit
whole spirograms from past test sessions to be displayed or printed,
ACOEM recommends that hard copies of tracings should be maintained
so that the technical quality of tests
can be examined when necessary.
This is particularly important for
clinics and practices that provide occupational health services, in which
providers of medical services may
change periodically. The capability
of examining volume-time curves to
check the end of test and flowvolume curves to check the beginning of exhalation is essential in
determining whether spirometry test
results are probably valid or reflect
obvious testing artifacts?2
Calibration tracings and records
support the validity of spirometry
tests conducted on a particular day
with a particular spirometer. Because
OSHA requires that medical records
be retained for 30 years after termination of employment/'" ACOEM
recommends that these calibration
records be saved and a log kept of
any problems found and solved or
any changes in protocol, computer
software, or equipment that were
made. Thermal paper should be photocopied because it fades rapidly
over time.
It is important to note that a new
National Institutes of Health-sponsored program, the National Lung
Health Education Program (NLHEP), is being developed to encourage primary care physicians to
screen smokers for chronic obstructive pulmonary disease.t! NLHEP
requires less rigorous testing procedures and documentation than are
required for occupational spirometry
testing and encourages the use of
new, inexpensive "office spirometers." Occupational medicine physicians must be cautioned that many of
NLHEP's testing procedures and
"office spirometers" are not acceptable for diagnostic spirometry or for
occupational screening, surveillance,
and impairment evaluations.
Testing Technique
OSHA,28 the Social Security Administration," the Federal Coal Mine
Health and Safety Act," and the
ATS 22 make specific recommendations regarding performance of the
forced expiratory maneuver and
measurement of the spirogram. Key
elements from the 1994 ATS Update
and changes from the 1987 ATS
guidelines are summarized below
and in Table 4.
Testing should be conducted at
ambient temperatures between 17°C
and 40°C. However, temperatures
~23°C are preferable to avoid a
large temperature difference between
spirometer temperature and body
temperature.V If a large difference
exists, the exhaled air cannot fully
cool down to the spirometer temperature within the first second of exhalation. In this case, an inappropriate
correction factor, based on the spirometer temperature, will usually be
selected to adjust the exhaled volume
from spirometer to body temperature
(body temperature and pressure saturated with water vapor [BTPS] correction), causing inflated measurements of BTPS-corrected FEV 1.42,43
The technician must demonstrate
correct performance of a spirometry
test, as well as describe it verbally. to
the subject being tested. The technician must enthusiastically coach the
subject to record "acceptable" maneuvers, which have good starts, are
free from artifacts, and have satisfactory exhalations (Table 4). Specifically, the subject must: (1) exhale
with a hard, fast "blast" of air so that
the volume of air leaked out before
the blast (the "extrapolated volume")
is less than 5% of the FVC, or 0.150
L, whichever value is greater; (2)
exhale smoothly, with no cough or
glottis closure in the first second, and
no leak, obstruction of the mouthpiece, or variable effort; and (3) exhale completely. for at least 6 to 10
seconds and/or until a l-second FVC
plateau is reached, unless the subject
cannot exhale for this long because
JOEM • Volume 42, Number 3, March 2000
233
TABLE 4
Spirometry Testing Technique
•
•
•
•
•
•
•
•
•
Test at ambient temperatures 17-40°C, with spirometer ~23°C, if possible.
Technician describes and demonstrates the test, and enthusiastically coaches the subject.
"Acceptable" maneuvers have good starts, are free from artifacts, and have satisfactory exhalations:
- exhale with hard, fast "blast" of air, with little air leaked out before the blast
- exhale smoothly, no cough or glottis closure in the first second, and no leak, obstruction of the mouthpiece, or variable effort
- exhale completely, for at least 6-10 sec and/or until an FVC plateau is recorded for 1 sec, unless subject must stop because of discomfort, airways obstruction, or old age.
Testing goal: Record at least three acceptable curves, with up to eight attempts if necessary; and achieve reproducibility of 0.20 L for
both the FVC and the FEV1 .
Test results can be interpreted even if they fail to meet testing goal (impaired subjects may have trouble); note that such results probably underestimate subject's true pulmonary function.
Obtain electronic or hard copies of tests to check "acceptability."
Check end of test using volume-time curves: FVC plateau and length of expiration.
Check start of test using flow-volume curves: flow rate should rise immediately to sharp peak.
As noted earlier, ACOEM strongly recommends that hard copies and/or electronic copies of complete spirograms be saved from all
spirometry test sessions.
of discomfort, airways obstruction,
or advanced age.
The testing goal is to record at
least three acceptable maneuvers
with the best PVC and the best FEY 1
reproduced to within 0.20 L, attempting up to eight maneuvers if
necessary.F Failure to meet these
criteria does not rule out interpretation of results, because some impaired subjects may have difficulty
in attaining them. 44-46 However,
when interpreting such results, it
must be borne in mind that tests
failing to meet the testing goal usually underestimate true pulmonary
function.
The need for electronic or hard
copies of a test session to support the
"acceptability" of the test session
cannot be overstated. Adequacy of
the end of test is best checked by
examining volume-time curves for
evidence of an PVC plateau and
length of expiration (Fig. 1). The
beginning of exhalation is best
checked by examining flow-volume
curves from each maneuver for an
immediate rise to a sharp peak in
expiratory flow rate (Fig. 2). Unacceptable spirograms are depicted in
the 1994 ATS Update/" and in some
reference books.'? Examination of
hard copy or electronic tracings is
probably the only way of evaluating
whether trends in spirometry test results are real or obviously reflect
testing artifacts. ACOEM strongly
recommends that hard copies andlor
electronic copies of spirograms be
saved from spirometry test sessions.
Measurement of Results
The largest PVC and the largest
FEY 1 from the acceptable curves are
reported for a subject, even if they
are not derived from the same maneuver (Table 5). Also, the largest
FEY 1 may come from a curve that is
acceptable except for its early termination.F All expiratory flow rates
are drawn from the single acceptable
tracing having the largest sum of
FEY l + PVC. Users should check
their spirometers to ensure that their
spirometry software selects the correct values for the test report. All
observed volumes and flow rates are
corrected to body temperature
(BTPS).
Technician Training
In 1978, OSHA prescribed elements of standardization for spirometry in the occupational setting when
it promulgated the Cotton Dust Standard. 28 The need for technician training is emphasized in the Preamble to
the Standard: "The key to reliable
pulmonary function testing is the
technician's way of guiding the employee through a series of respiratory
maneuvers. The most important
quality of a pulmonary function tech-
mcian is the motivation to do the
very best test on every employee.
The technician must also be able to
judge the degree of effort and cooperation of the subject. The test results
obtained by a technician who lacks
these skills are not only useless, but
also convey false information which
could be harmful to the employee."
On the basis of the "Qualifications
of personnel administering the test"
given in Appendix D of the Cotton
Dust Standard, NIOSH developed a
program that reviews and approves
spirometry training courses. Cotton
Dust Standard Appendix D outlines
the content of NIOSH-approved spirometry courses and states that the
goal of these courses is to provide
technicians with "the basic knowledge required to produce meaningful
results." For many exposures, OSHA
requires that technicians attend
courses "sponsored by an appropriate academic or professional institution" or a NIOSH-approved
course,z8,47,48 Although attendance
at a NIOSH-approved course is not
required for technicians outside of the
cotton industry, most companies view
NIOSH approval as minimal assurance
that the course will adequately teach
the basic principles of spirometry.
NIOSH currently approves about one
course per year; 50 courses that have
been approved are currently active.
ACOEM,49 NIOSH,43 ATS,22 and
Spirometry • Occupational and Environmental Lung Disorder Committee
234
TABLE 5
Measurement of Results and Technician Training
Measurement of results
• Report largest FVC and largest FEV1 from acceptable curves even if not on same curve.
• All expiratory flow rates come from one acceptable tracing with largest sum of FEV1 + FVC.
• Check your spirometer to be sure correct values are selected for test report.
• Correct all observed volumes and flow rates to body temperature (BTPS).
Technician training
• From Preamble to OSHA Cotton Dust Standard, 1978:
"The key to reliable pulmonary function testing is the technician's way of guiding the employee through a series of respiratory maneuvers;
The most important quality of a pulmonary function technician is the motivation to do the very best test on every employee;
The technician must also be able to ludqe the degree of effort and cooperation of the subject;
Test results obtained by a technician who lacks these skills are not only useless, but also convey false information which could be
harmful to the employee." [emphasis added]
•
•
•
ACOEM strongly recommends that spirometry technicians in the occupational setting complete a NIOSH-approved spirometry
course as part of their training.
ACOEM recommends that technicians attend spirometry refresher courses every 3 years.
If feasible, a program providing periodic quality assurance review of spirograms is highly recommended.
the American Association of Occupational Health Nurses'" all recommend technician training to ensure
accurate pulmonary function testing.
Spirometry refresher classes are
not mandated by any OSHA regulations, nor does NIOSH approve the
content of refresher courses. However, the need for repeated training
of technicians was recognized and
documented in the National Institutes of Health-sponsored multicenter Lung Health Study3 7 and the
NIOSH-monitored spirometry of the
third National Health and Nutrition
Examination Survey (NHANES
111),38 and ACOEM has recommended "periodic, eg, every 3
years," refresher courses for many
years." Spirometry refresher courses
keep technicians informed of
changes in occupational pulmonary
function testing and reinforce the
need for vigilance in conducting spirometry tests. Technician drift and
apathy develop if no feedback is
provided on test quality, and on the
importance of active coaching and
recognition of testing errors. Intensive refresher courses designed for
experienced technicians are recommended instead of attending part of a
NIOSH-approved spirometry course.
The 1994 ATS Update strongly
emphasizes the importance of tech-
nical quality in achieving valid spirometry results; figures showing
many technical errors that plague
spirometry testing are presented in
the Update." ATS recommends that
spirograms be reviewed periodically
to provide regular feedback on the
quality of each technician's testing.
Quality control reviews can be performed on tracings that are saved
electronically during the testing session or on photocopies of randomly
selected spirograms.
As summarized in Table 5,
ACOEM strongly recommends that
spirometry technicians in the occupational setting complete a NIOSHapproved spirometry course as part
of their training. Increasingly, clinics
and practices engaged in providing
occupational medical services may
argue that such training is not needed
for adequate performance of the test.
However, recognition of the technical pitfalls of spirometry is critical in
the occupational area, and NIOSHapproved courses are specifically
geared toward training technicians to
conduct screening spirometry tests
and to recognize these pitfalls. In
addition, ACOEM continues to recommend that technicians attend spirometry refresher courses every 3
years to discuss testing problems.
Such courses encourage technicians
to remain vigilant and enthusiastic
during spirometry testing of workers.
If feasible, a program providing
quality assurance review of spirograms is also highly recommended.
Interpretation of Results
Interpretation of spirometry results
should always begin with an assessment of test quality.22 Once the validity of the measurements has been
established, evaluation of the test
subject's lung function can proceed.
Interpretation of results is summarized in Tables 6 and 7 and Fig. 3.
Selection of Reference Values
The first step in interpreting pulmonary function results is usually to
determine where the subject's spirometry values fall relative to the
normal range. Ideally, this normal
range would be based on a population similar to the workers being
examined, with spirometry measurements made and analyzed in accordance with the most recent ATS
recommendations, using equipment
and testing technique similar to that
employed in testing the workers under consideration.P However, reference "predicted" values that define
the normal range are often drawn
from relatively small numbers of
JOEM • Volume 42, Number 3, March 2000
235
TABLE 6
Selection and Race-Adjustment of Reference Values
Selection of reference values
• Pulmonary function related to age, height, and sex in an asymptomatic non-smoking reference group; summarized in regression
equations, usually named after the primary investigator.
• To check the fit of reference values to a particular setting, ATS recommends testing 20-40 local, non-smoking healthy subjects and
determining their % of predicted using the intended reference equations.
• Knudson prediction equations widely used in the occupational setting because Knudson's 1976 equations were mandated by OSHA
Cotton Dust Standard in 1978.
• Knudson data re-analyzed in 1983 to conform to ATS recommendations: changed predicted values considerably, particularly for
forced expiratory flow rates.
• Crapo prediction equations adopted as standard reference by the AMA Guides to the Evaluation of Permanent Impairment, 4t h ed.,
1995.
In January 1999, equations specific for Caucasians, African-Americans, and Hispanics were published from the NHANES III, based
on a random sample of the US population.
• ACOEM recommends that occupational settings consider adopting NHANES III equations for general use as they become available
in spirometry systems, unless testing is conducted under a regulation/guideline that requires other reference values.
Race adjustment of predicted values
• Race-adjustment of Caucasian predicted values for African-Americans has been widespread in the occupational setting since 1978,
when the OSHA Cotton Dust Standard mandated that Caucasian predicted FEV1 and FVC be multiplied by 0.85 for African-Americans to adjust for ethnic differences.
• ATS recommends using race-specific prediction equations such as NHANES III, if possible, or using a 0.88 scaling factor to raceadjust Caucasian predicted values for African-Americans.
• Use subject's self-declared race or ethnic group as a basis for race-adjusting or selecting race-specific predicted values.
• Less consensus on adjustment of predicted values for non-Caucasian ethnic groups other than African-Americans.
• Until NHANES III equations become widely available, ACOEM recommends cautious race-adjustment of Caucasian predicted FEV1
and FVC for African-American, Chinese, and Japanese subjects using ATS scaling factor of 0.88, unless testing under a regulation/
guideline that requires specific race-adjustment factors.
•
subjects resident in a single geographic location, often near or accessible to an interested research investigator. Reference values may be
derived from an institutional or occupational group, a population-based
epidemiologic study, or subjects chosen specifically to create reference
equations.P Within the study group,
the relationship between pulmonary
function and age, height, and sex is
summarized in regression equations,
which are usually named after the
primary investigator. In clinical medicine, many laboratories use the
equations of Morris et al,51 Crapo et
al,52 or Knudson et al,53 depending
to some degree on which equations
are programmed into the automated
spirometry equipment."
In the occupational setting, Knudson's prediction equations have been
widely used because the 1976 equations55 were mandated by the OSHA
Cotton Dust Standard: they were the
only equations available at the time
that studied both male and female
subjects, were based on non-smokers, and used back-extrapolation to
define time zero. The data of Knudson et al were re-analyzed in 198353
using data selection criteria that conform to ATS recommendations, resulting in equations that predict considerably different values than in
1976, particularly for the forced expiratory flow (FEF) rates. Crapo's
prediction equations'f are also used
in the occupational setting because
they were adopted by the American
Medical Association as the standard
reference in the 4 th Edition of the
American Medical Association
Guides to the Evaluation of Permanent Impairment.' Many reference
equations are listed in the ATS Interpretative Statement." and the 1997
NIOSH Spirometry Training Guide
demonstrates the varying results obtained when different prediction equations are used." As recommended by
the ATS, the fit of a set of reference
values to a particular occupational setting can be checked empirically by
testing 20 to 40 local, non-smoking
healthy subjects and determining their
percentages of predicted using the intended reference equations.23
It should be noted that an important alternative source of spirometry
reference values has recently become
available for both the clinical and the
occupational settings. In January
1999, race/ethnic group-specific
equations were published from the
NHANES ill, based on a random
sample of the US population and
using standardized, state-of-the-art
spirometry testing rnethodology/"
The NHANES ill data permitted reference equations to be calculated
separately for Caucasians, AfricanAmericans, and Hispanics. Although a
few regulations and guidelines continue to require the use of specific sets
of reference values,8,9,28 ACOEM recommends that the NHANES ill equations be considered for general use in
the occupational setting as these equations become available in computerized spirometry systems.
Race Adjustment of Predicted
Values
Publication of the NHANES ill
prediction equations is an important
236
TABLE 7
Interpreting Results: Lower Limit of
Normal (LLN) and Flow Rates
LLN
• Use 5t h percentile LLN instead of
80% of predicted to classify employees as "normal" or "abnormal"; because 5t h percentile LLNs tend to
decline with age, largest difference
will be seen for older workers.
• Obtain 5t h percentile LLN from same
reference group as predicted values,
from tables or equations in the reference, or calculate LLN = 1.645 x
SEE.*
Interpreting forced expiratory flow rates
• FEF2 5-7 5 % and instantaneous flows
should not be used to diagnose
small airway disease in individuals or
to assess respiratory impairment because of the wide variability in flow
rates within and between healthy
subjects.
• If FEV1 and FEV/FVC are in the normal range, FEF2 5-7 5 % and other flow
rates should not be interpreted, although an FEF2 5-75 % percent of predicted <LLN can be used to confirm
the presence of airways obstruction
in the presence of a borderline FEV/
FVC.
• Flow rate variability determines the
5th percentile LLN for the FEF2 5-7 5 % '
Using Knudson's 1983 reference values, the 5th percentile LLN for
FEF2 5-7 5 % for a man 40 years or
older is 40.3% of predicted. If such a
man's observed FEF2 5-7 5 % is half of
his predicted value, he is still within
the normal range.
* SEE, standard error of estimate.
Spirometry • Occupational and Environmental Lung Disorder Committee
o
Check test quality
Is FEV.fFVC %pred
Is FEV1 %pred
~
~
LLN?
LLN?
Yes =l>
NOT OBSTRUCTED
Ye s=l>
Possible Borderline
Obstruction
Ye s=l>
Mild Obstruction
=l> Go to
e
.
No~
Is FEYI (60 o/opred- < LLN)?
No.u.
IsFEYI (41- 59 %pred)?
Y es =l>
Moderate Obstruction
Is FEV1 s 40 %pred
Y es =l>
Severe Obstruction
FVC %pred ~ LLN?
-Yes
No1l
Mixed Obstructivel
Restrictive Pattern
[Reduced FVC may be
due to air trapping.]
Is PVC %pred
~
LLN?
Yes =l>
NOT RESTRICTED
No1l
Is PVC (60 %pred - < LLN)?
Yes =l>
Mild Restriction
Yes =l>
Moderate Restriction
Yes =l>
Severe Restriction
No~
Is PVC (51 - 59 %pred)?
Nolj.
Is PVC s 50 %pred ?
SeeText
Fig. 3. Spirometry interpretation flowchart. LLN, lower limit of normal.
step forward, not only because the
reference values are based on a random sample of the US population
that was examined in the past few
years, but also because predicted values specific for African-Americans
and Hispanics, based on randomly
selected subjects from the US population, are now available. Until this
time, the most widely used reference
values have been derived from Caucasian populations in North America.
Before 1978, when workers in the
cotton industry were evaluated using
these reference values for Caucasians, more abnormal spirometry results were noted among AfricanAmerican than among Caucasian
workers. Because race-specific reference equations were not in general
use in 1978, OSHA mandated that
"the predicted FEV 1 and FVC for
blacks should be multiplied by 0.85 to
adjust for ethnic differences" (Table
6). At the time, OSHA recognized that
"this correction may not be precisely
correct," but it relied on the current
state-of-the-art "to provide proper interpretation of spirometry measurements for blacks without inadvertently
fostering discrimination in hiring practices.28 " The practice of adjusting
Caucasian predicted values for FVC
and FEV 1 for African-American sub-
jects has remained widespread in the
occupational setting since 1978. However, race-adjustment is less widely
used in the clinical setting. 54
The 1991 ATS Official Statement
on "Lung Function Testing: Selection of Reference Values and Interpretative Strategies" recommends
use of race-specific prediction equations such as the NHANES m5 6 if
"possible and practical," or cautious
use of a scaling {"race-adjustment"}
factor of 0.88 if non-Caucasians are
tested infrequently.F It is important
to use a subject's self-declared race
or ethnic group as a basis for select-
237
JOEM • Volume 42, Number 3, March 2000
ing appropriate race-specific predicted values or for deciding whether
or not to race-adjust Caucasian predicted values. Although using raceadjusted Caucasian predicted values
for African-American subjects is
preferable to using non-adjusted
Caucasian predicted values,57 recent
studies conclude that a single adjustment factor is not optimal and that
race-specific equations should be
used. 57.58
There is less consensus on the
adjustment of Caucasian predicted
values for other ethnic groups, such
as Hispanics, Asians, and Pacific Islanders, than there is for AfricanAmericans." Current sources and
studies do not recommend raceadjustment for any of these groups
except for some Asian and Oriental
groups (eg, Chinese and Japanese) in
addition to African-Americans.Vr"
As noted above, ACOEM recommends that occupational settings
consider adopting the NHANES ill
equations for general use as they
become available in spirometry systems. Until these equations are available, ACOEM recommends that
Caucasian predicted values be raceadjusted for African-American, Chinese, and Japanese subjects, applying
the ATS recommended scaling factor
of 0.88 to the Caucasian predicted
FEY 1 and PVC (Table 6). However, if
testing is conducted under the few
regulations and guidelines that have
specific recommendations/requirements regarding race-adjustment factors,8,9,28 those requirements should be
followed.
Cross-Sectional Evaluation:
Normal, Obstructed, Restricted
In its 1991 Interpretation Statement, the ATS recommends that spirometry results be interpreted on the
basis of a stepwise algorithm using
very few parameters.Pr'" as summarized in Fig. 3. A value of the FEY /
PVC percent of predicted below the
lower limit of normal (LLN) indicates probable obstructive impairment. Having established the pres-
ence of obstruction, the FEY1
percent of predicted is used to grade
the degree of obstructive impairment. There are several definitions of
severity categories available,9.l0,23,30
and Fig. 3 presents the ATS respiratory impairment categories,'? which
define "mild" obstruction as an
FEY1 between 60% of predicted and
the LLN, "moderate" obstruction as
an FEY1 of 41% and 59% of predicted, and "severe" obstruction as
an FEY1 of 40% or less of predicted.
"Borderline" obstruction may exist
when a subject's FEY1IFVC percent
of predicted is below its LLN but the
FEY1 falls within the normal range.
However, the ATS cautions that "the
pattern of a low FEY IIFVC ratio and
greater than average PVC and FEY1
should be recognized as one that may
occur in healthy individuals't.P
In the absence of airways obstruction, the PVC percent of predicted is
used to determine whether restrictive
impairment is present, with the ATS
defining "mild" restriction as an
PVC between 60% of predicted and
the LLN, "moderate" restriction as
an PVC of 51% and 59% of predicted, and "severe" restriction as an
PVC of 50% or less of predicted. 10
Contrary to long-standing practice,
the use of a fixed cutoff of 80% of
predicted as LLN is not recommended (Table 7) and should be
replaced by the fifth percentile, the
point below which 5% of normal
subjects fall. 23 The LLN should be
obtained from the same source as the
predicted values, from tables or
equations presented in the reference,53,56 or calculated as: LLN =
1.645 X SEE (standard error of estimate),z3 LLNs calculated in this way
tend to decline with age and thus can
have an impact on whether a 50- to
60-year-old employee is labeled as
"normal" or "abnormal." For example, by using the 1983 Knudson prediction equations.P the LLN (5th
percentile) for PVC for a man of 40
years or older is 73.4% of predicted,
which is significantly below the previously used 80% of predicted.
Finally, because of the wide variability within and between healthy subjects, the ATS states that
"FEF25-75% and the instantaneous
flows should not be used to diagnose
small airway disease in individual
patients'f" or to assess respiratory
impairment. 10 Interpretation of
FEF25-75% and other flow rates is not
recommended if the FEY1 and the
FEY IIFVC are within the normal
range, although the flow rates "may
be used to confirm the presence of
airway obstruction in the presence of
a borderline FEY INC.,,23 In other
words, an FEF 25-75% percent of predicted below its LLN can confirm
the presence of airways obstruction
in subjects falling into the "Possible
Borderline Obstruction" category in
Fig. 3. However, such interpretations
should bear in mind the ATS's warning that a low FEY IIFVC ratio accompanied by PVC and FEY1 that
are above average, ie, > 100% of
predicted, can occur in healthy individuals.F'
The degree of variability in the
FEF25_75% is reflected in the low
value of its 5th percentile LLN. Using the 1983 Knudson prediction
equations, the 5th percentile LLN for
FEF25_75% for a man of 40 years or
older is 40.3% of predicted, indicating that a man over 40 must be less
than half of his Knudson predicted
value before he falls below the normal range.
Changes Over Time
In the occupational setting,
changes over time in pulmonary
function should be examined for two
reasons: (1) to evaluate a worker's
response to treatment in the clinical
setting, and (2) to screen healthy
workers for excessive loss of function over time. In the first situation,
the ATS recommends a non-algorithmic approach to interpretation, stating that "the clinician seeing the
patient can often interpret results of
serial tests in a useful manner, not
reproducible by any simple algorithm. For example, seemingly stable
tests may prove very reassuring in a
238
Spirometry • Occupational and Environmental Lung Disorder Committee
patient receiving therapy for a disease that is otherwise rapidly progressive. The same tests may be very
disappointing if one is treating a
disorder that is expected to improve
dramatically with the therapy prescribed. Depending on the clinical
situation, statistically insignificant
trends in function may be very meaningful to the clinician.'m
The second situation, screening
healthy workers for excessive loss of
pulmonary function, is often encountered in workplace medical surveillance programs. When subjects' spirometry test results are compared
with a cross-sectional LLN, as described in the previous section and
shown in Fig. 3, excessive loss of
pulmonary function will be identified adequately in workers with average or less than average lung size.
However, such evaluations will not
detect early excessive loss of function in workers whose lung size is
above average, ie, above 100% of
predicted. Particularly for these subjects, change in pulmonary function
over time should be included in a
screening program to determine
whether the worker's spirometry test
results are decreasing faster than expected over time. 23,36,60
Loss of FEV1 or PVC over time
can be estimated simply by calculating the difference between volumes
measured at two points in time, or by
fitting a least squares "slope"
through periodic measurements over
time for an individual. Because estimates of individual rate of change
become more precise as follow-up
time increases, loss of FEV1 or PVC
should be estimated from measurements made over a minimum of 4 to
6 years. 61-64 Measurement frequency has less impact on precision
than length of follow-up does,61,62
but periodic measurements are
needed to detect workers experiencing rapid declines in pulmonary
function and to detect systematic differences between examinations over
time.62,64
Interpretation of change over time
in the screening setting is compli-
cated by the substantial variation in
rates of change that exist both between workers and within an individual worker. Although the FEV1 and
PVC can be measured precisely during one test session, biologic and
technical variation over time make
an individual's estimated rate of
change over time highly variable.61-65 Although within-day variability for a normal subject's FEV1
and PVC is :s; 5%, year-to-year variability is :s; 15%.23,62 Technical variability can be minimized by using
very precise spirometers, not changing equipment unnecessarily over
time, and maintaining a rigorous spirometry quality assurance program,
Biologic variability can be reduced
by conducting successive spirometries at about the same time of day
and in the same month each year.
Because of the precision gained by
combining results from many subjects, group estimates of change can
be calculated and comparisons made
between groups in epidemiologic
studies.
Epidemiologic data have indicated
that for adult smokers "to develop
clinically significant airflow obstruction, the average rate of decline of
FEV 1 ... probably needs to be
greater than 90 mlIyear, or about
three times that seen in non-smokers
and twice the rate seen in the 'nonsusceptible' smokers".65 One study
found that about 4% of their combined smoking and non-smoking
male population had FEV1 slopes of
100 mL/year or greater when calculated over 4 to 11 years of followUp.66 However, studies differ in their
estimates of change over time, and,
to date, neither longitudinal predicted values nor 5th percentile LLNs
have been recommended for the
evaluation of individual rates of
change over time in occupational or
clinical settings. 62
To meet the need for longitudinal
LLNs, the ATS recommends a conservative strategy to minimize false
positives in the screening setting,
stating that: "The greatest errors occur when one attempts to interpret
serial changes in subjects without
disease because test variability will
usually far exceed the true annual
decline, and reliable rates of change
for an individual subject cannot be
calculated without prolonged followup. Thus, in subjects with "normal"
lung function, changes in PVC or
FEV 1 over 1 year should probably
exceed 15% before any confidence
can be given to the opinion that a
meaningful year-to-year change has
occurred.',23 NIOSH adopted this
definition of significant change in a
1995 Criteria Document, stating that
"because of considerable short-term
variability in FEV1, a year-to-year
change of greater than 15% should
occur before a change in FEV1 is
considered significant." NIOSH concluded that "evidence of impaired
lung function is present when there is
a confirmed finding of a decline in
FEV1 (adjusted for the expected interval decline in FEV 1) of 15% or
greater" and that such a decline "is
considered significant and warrants
further medical evaluation'V"
Because FEV1 and PVC decline
with age from the about the mid-30s
on, with some acceleration of the rate
as aging advances,68,69 an allowance
for the expected loss due to aging
should be made before labeling a
15% decline as "significant.,,36,67 As
Appendix G of the NIOSH Criteria
Document'" states: "The LLN for the
follow-up FEV1 is computed by taking 85% of the baseline value minus
the expected decline over the time
period. An individual's expected decline over the time period is dependent on histher age, but for practical
considerations, a constant value of
25 mllyear is often recommended.
For example, an individual whose
initial FEV1 is 4.00 L would be
considered to have an accelerated
decline in FEV 1 if histher FEV1 is
below 3.15 L, 10 years after the
baseline value was determined
[(0,85 X 4.0 L) - (10 years X 0.025
Uyear) = 3,15 L]." Such a loss over
10 years would be labeled "significant" and would warrant medical
JOEM • Volume 42, Number 3, March 2000
239
TABLE 8
Changes Over Time and Bronchodilator Response
Changes over time
• In secondary prevention of respiratory disease, medical surveillance programs look for excessive loss of lung function over time as
an early sign of lung function impairment.
• Small changes over time will not be detectable if the spirometer and testing technique are not as accurate, precise, rigorous, and
standardized as possible.
• The highest degree of spirometer accuracy and precision is needed for serial spirometry measurements.
• Estimated rates of change over time for individuals are highly variable and should be calculated using at least 4-6 years of test results to increase the precision of the estimate.
• ACOEM recommends conducting spirometry every 1-2 years when indicated because of workplace exposures, unless otherwise
specified by applicable regulations or recommendations. Test frequency may vary with age as in the National Fire Protection Association examination protocol, which recommends spirometry testing every 3 years for those under age 29, every 2 years for ages 3039, and annually for ages 40 and above.
• Interpretation of change over time is complex:
- In the clinical setting, the ATS states that "the clinician seeing the patient can often interpret results of serial tests in a useful manner, not reproducible by any simple algorithm." Depending on the clinical situation, seemingly stable tests may indicate treatment
success or failure.
- When screening subjects with "normal" lung function, ACOEM recommends that: (1) an FEV1 or FVC decrease of 90-100 mUyear,
calculated over at least 4-6 years, should trigger further scrutiny of pulmonary function over time; or (2) loss of 15% or more of
the baseline observed FEV1 or FVC, adjusted for the expected interval decline due to aging, should be regarded as "significant." If
the low results are confirmed on a re-test, a medical review is warranted, even if the worker's values still remain above the crosssectional LLN.
Pre- to post-bronchodilator changes in pulmonary function
• ATS and the National Heart, Lung, and Blood Institute's National Asthma Education and Prevention Program consider a pre- to postbronchodilator increase of ~12% of initial FEV1 and ~0.2 L to be significant.
• Attention should focus on FEV1 because varying lengths of expiration may complicate changes in FVC or FEF2 5-75 % ' If examined,
initial FVC should change by ~15% to be considered significant. Pre- to post-bronchodilator changes in the FEF2 5-75% should not
be interpreted.
• Failure to achieve such responses to bronchodilators in the laboratory does not completely exclude the possibility of reversible airways disease.
• The best values for FVC and FEV1 should be used in impairment determinations, whether recorded before or after bronchodilator administration.
evaluation once the low value was
confirmed by are-test. 36,67
In summary, as shown in Table 8,
ACOEM recommends that spirometry be conducted every I to 2 years
when indicated because of workplace exposures, unless otherwise
specified by applicable regulations
or recommendations. The frequency
of testing may vary with age and
length of exposure, as in the National
Fire Protection Association examination protocol, which recommends
spirometry testing every 3 years for
firefighters under age 29, every 2
years for ages 30 to 39, and annually
for ages 40 and above.?" Change in
FEV 1 and PVC over time should be
evaluated as part of a screening program once measurements have been
made over at least 4 to 6 years. A
decrease in FEV 1 or PVC of 90 to
100 mUyear, calculated over at least
4 to 6 years, should trigger further
scrutiny of a worker's pulmonary
function measurements over time.
Loss of 15% or more of the baseline
observed FEV 1 or PVC, after allowing for the expected decrease due to
aging, should be regarded as a significant decline over time. If the low
results are confirmed on a re-test, a
medical review is warranted, even if
the worker's values still remain
above the cross-sectional LLN.
Pre- to Post-Bronchodilator
Changes in Pulmonary Function
The ATS 2 3 ,71 and the National
Heart, Lung, and Blood Institute's
National Asthma Education and Prevention Program72 recommend that a
pre- to post-bronchodilator increase
in FEV 1 should be at least 12% of
initial FEV 1 and at least 0,2 L to be
called significant, ie, a bronchodilator response that is suggestive of
airways hyperreactivity (Table 8).
The Global Initiative on Asthma"
and the National Heart, Lung, and
Blood Institute Lung Health Study?"
regarded a 15% increase in FEV 1 as
significant.
Attention should be limited to
changes in the FEV 1 because interpreting changes in the PVC or FEF 25- 75 %
is likely to be complicated by varying
lengths of expiration recorded before
or after the bronchodilator. 23 If
changes in the PVC are examined, the
ATS recommends that a change of at
least 15% of initial PVC be considered
significant, ie, suggestive of airway
reactivity. The ATS does not endorse
interpretation of pre- to post-bronchodilator changes in the FEF25 _75 0/0 ,z 3
On the basis of these sources,
ACOEM recommends that a pre- to
post-bronchodilator increase in
FEV 1 should be at least 12% of
initial FEV 1 and at least 0.2 L to be
considered significant, ie, suggestive
of reversible obstructive airways disease. However, it should be noted
240
Spirometry • Occupational and Environmental Lung Disorder Committee
TABLE 9
Acute Work-Related Changes in FEV1 and PEF
•
•
•
•
•
•
•
•
Work-related bronchoconstriction can decrease FEV1 across a work shift or increase variability in PEF rates across a longer period at
work, particularly in occupational asthma.
When evaluating FEV1 decrease across a work shift, spirometer temperature should be ~23°C (73°F) for pre- and post-shift tests to
avoid an artificial FEV1 decline due to faulty BTPS correction of the pre-shift FEV1 •
ACOEM recommends that: (1) a single pre- to post-shift FEV1 decline of ~10% is worthy of follow-up; and (2) an across-shift FEV1 decline of ~5% or 0.2 L, whichever is greater, seen on at least two occasions, should be followed up but interpreted cautiously, inasmuch as comparable Within-day variability can be seen in normal subjects.
Serial PEF monitoring can be used to confirm suspected associations between a worker's respiratory symptoms and exposures on the
job, and to identify potential triggering exposures.
A protocol like the following should be used for serial PEF monitoring:
- at least 4 times/day, three PEF measurements should be made and the highest of the three analyzed, with one measurement made
on first awaking, and others made at noon, after work, and before bedtime for a day shift worker; and
- if possible, workers should be monitored for ~2 weeks at work and for 2 weekends to 10 days away from work, as needed, to identify or exclude work-related changes in PEF.
Evaluate serial PEF measurements:
- by calculating daily variability, with a mean diurnal variation ~20% probably indicating asthma; and
- expert visual inspection of graphs of maximum, mean, and minimum daily PEFs is a more sensitive and specific evaluation technique; work is ongoing to quantify these qualitative expert judgments.
Factors that can interfere with interpretation include reliance on self-reporting by the monitored worker, intermittent exposure to suspect agents in the workplace, delayed measurement of PEF when waking on days off, and use of multiple PEF meters.
ATS recommends levels of accuracy and precision for peak flow meters, and peak flow meters have been evaluated; portable spirometers are also emerging for serial spirometry tests.
that failure to achieve such a response to bronchodilators in the laboratory does not completely exclude
the possibility of reversible airways
disease. ACOEM also concurs with
the ATS 10 and the American Medical
Association" that impairment determinations should use a worker's best
values for PVC and FEV l , whether
recorded before or after bronchodilator administration.
Acute Work-Related Changes in
Pulmonary Function
Work-related bronchoconstriction,
causing decreased pulmonary function across a work shift or increased
variability in pulmonary function
across a longer period at work, can
be elicited by bronchial irritants and
sensitizers and is often reversible.
Patterns of work-related change are
an important element in the diagnosis of a number of occupationally
related respiratory disorders, particularly occupational asthma (Table 9).
Spirometry measurements should be
made as close to the work environment as possible to avoid a long time
lapse between the worker's occupational exposure and the measurement
of pulmonary function. As discussed
below, when occupational asthma is
suspected, additional measurements
should also be made at home at the
conclusion of the workday to capture
any delayed work-related declines in
function. The spirometry measurements most commonly examined are
the FEV 1 and the peak expiratory
flow (PEP) rate, although interpretation of FEV 1 decline is better standardized than interpretation of PEF
variability. Newly marketed portable
spirometers are becoming available
for serial spirometry measurements
in the workplace in addition to the
traditionally used peak flow meters.
In 1978, the OSHA Cotton Dust
Standard defined an across-shift decrease in FEV 1 of 5% or 0.2 L,
whichever is greater, as a significant
drop if confirmed within 1 month."
In 1986, a drop in FEV 1 of 5% or
0.15 L, whichever is greater, was
labeled as significant, if confirmed
on a second occasion/" An FEV 1
decrease of 10% would be considered significant if only one pre- to
post-shift study was performed. 60.75
When considering such small declines in FEV 1 as significant, it is
critical to maintain the testing environment and the spirometer at 23°C
(73°F) or above. 42 ,4 3 FEV 1 declines
of several percent can be produced as
an artifact if the testing environment
and the spirometer warm up by several degrees between the pre- and
post-shift tests. Usually the BTPS
correction factor is selected on the
basis of the spirometer temperature,
and not the temperature of the accumulated exhaled gas I second after
the expiration commences. With a
cold pre-shift spirometer, a large
BTPS correction factor may be applied to exhaled air that is still closer
to body than to spirometer temperature, resulting in an inflated "observed" FEV I' With a warmer postshift spirometer, the temperature of
the accumulated exhaled air is closer
to the spirometer temperature so that
the selected BTPS factor is appropriate. Subsequently, calculation of a
pre- to post-shift change in FEV 1
finds an FEV 1 decline that depends
on the warming of the spirometer
across the work shift rather than
employee exposures in the work environment."
On the basis of the sources described above, ACOEM recommends that a single pre- to post-shift
study finding a decline in FEV 1 of at
242
Spirometry • Occupational and Environmental Lung Disorder Committee
Throughout this position statement, ACOEM makes detailed recommendations to ensure that each of
these areas of test performance and
interpretation follow current recommendations/standards in the pulmonary and regulatory fields.
Submitted by the Occupational
and Environmental Lung Disorder
Committee on November 16, 1999.
Approved by the ACOEM Board of
Directors on January 4,2000. At the
time of the preparation of this position statement, Occupational and Environmental Lung Disorder Committee members were:
James E. Lockey, MD, MS, Chair
Henry Velez, MD, Vice Chair
Arch 1. Carson, MD, PhD
Clayton T. Cowl, MD, MS
George L.Delclos, MD, MPH
Bret J. Gerstenhaber, MD
Philip I. Harber, MD, MPH
Edward P. Horvath, MD, MPH
Athena T. Jolly, MD, MPH
Shadrach H. Jones, N, MD
Gary G. Knackmuhs, MD
Larry A. Lindesmith, MD
Thomas N. Markham, MD, MPH
Lawrence W. Raymond, MD, SM
David M. Rosenberg, MD, MPH
David Sherson, MD
Dorsett D. Smith, MD
Mary C. Townsend, DrPH
Stephen F. Wintermeyer, MD, MPH
Acknowledgments
The authors thank Drs John L. Hankinson
and Robert O. Crapo for many helpful suggestions and comments regarding this position statement. In addition, we thank the other
members of the American Thoracic Society
who shared their views and insights as this
position statement was developed.
Appendix: Glossary of Terms
and Abbreviations
ATPS: Ambient temperature and
pressure saturated with water vapor.
Volumes read directly off the volume-time spirogram are at ATPS.
Back extrapolation: In the calculation of FEV l' a method for determining the time zero. A straight line
is drawn through the steepest portion
of the volume-time curve back to the
baseline. Where this straight line intersects the baseline is the zero point
for timing the FEV iBest curve: The curve that gives
the largest sum of FEV 1 and PVC.
The best curve is used in the calculation of the FEF 25- 75 % and the instantaneous flow rates. In contrast,
the largest PVC and the largest FEV 1
are reported for the test session, even
if they are not from the same curve.
BTPS: Body temperature and
pressure saturated with water vapor.
All spirometric volumes and flows
must be corrected to BTPS.
Calibration check: Periodic determination of a spirometer's ability
to accurately measure volume. Calibration checks should be performed
at least daily using a 3-L syringe.
The instrument should maintain an
accuracy of :!:3% of the reading.
Additional checks include checking
for leaks (daily for volume spirometers) and, every 3 months, verifying
the accuracy of a timed chart and
checking the linearity of volume recording.
End of test: That point during the
forced expiratory maneuver when a
plateau at least 1 second long is
noted on the volume-time tracing.
Extrapolated volume: The volume determined by a line drawn
through the zero time point perpendicular to the baseline on a volumetime curve. The extrapolated volume
is read where this perpendicular line
intersects the volume curve; it should
be less than 5% of the PVC or 150
mL, whichever is greater.
FEVlIFVC%: Forced expiratory
volume in one second expressed as a
percentage of the forced vital capacity.
Flow-measuring spirometer: Indirectly measures volume of exhaled
air by measuring the rate at which air
is exhaled and deriving the volume.
Examples include pneumotachometer, mass flow, and turbine instruments.
Forced expiratory volume in one
second (FEV l): Volume of air ex-
haled during the first second of the
PVc.
Forced expiratory volume in six
seconds (FEV6 ) : Volume of air exhaled during the first six seconds of
the PVC. Because it is easier for
obstructed subjects to reach the
FEV6 than the PVC, there is growing
interest in measuring the FEV 6 and
the FEVllFEV6 in screening spirometry.
Forced expiratory maneuver:
Technique during spirometry in
which the subject takes the deepest
possible inspiration from a normal
breathing pattern and blows into the
mouthpiece as hard, fast, and completely as possible. Also known as
the forced vital capacity maneuver.
Forced vital capacity (FVC):
The maximal volume of air exhaled
from the point of maximal inspiration using a maximally forced expiratory effort.
Mean forced expiratory flow
during the middle half of the FVC
(FEF25-75%): Average flow rate
over the middle half of the expiration. Formerly called the maximal
mid-expiratory flow rate (MMEF).
Predicted normal values: Expected values for various lung volumes and flow rates derived from
healthy populations.
Reproducibility: In the absence
of disease-related changes, the ability of a test to obtain the same result
from an individual repeatedly tested
over a period of time. Reproducibility of the FEV 1 and PVC within a
test session should be 0.20 L or less.
Residual volume: Volume remaining in the lungs following a
maximal expiration.
Spirogram: A graphic recording
of a forced expiratory maneuver, as
either a volume-time or flowvolume tracing.
Spirometer: An instrument for
measuring lung volumes and flow
rates.
Total lung capacity: Total lung
volume following a maximal inspiration.
Valid test: A spirometry test consisting of at least three acceptable
243
JOEM • Volume 42, Number 3, March 2000
forced expiratory tracings for which
the best PVC and the best FEV1 are
reproduced within 0.2 L.
Volume-measuring spirometer:
Spirometers that directly accumulate
and measure the volume of exhaled
air as a function of time. Examples
include water-seal, dry rolling seal,
and bellows instruments.
Zero time point: In the measurement of FEVl ' the point selected as
the start of the test.
References
0 .•
,::
1. Harber P, Lockey JE. Pulmonary function testing in pulmonary prevention.
State ofArt Rev Occup Med. 1991;6:6979.
2. American Thoracic Society. Respiratory
protection guidelines. Am J Respir Crit
Care Med. 1996;154:1153-1165.
3. Boehlecke BA. Respirators. In: Harber P,
Schenker MB, Balmes JR, eds. Occupational and Environmental Respiratory
Disease. St Louis, MO: Mosby; 1996:
963-971.
4. US Code of Federal Regulations. Respiratory Protection. 1998. Title 29, Part
1910.134 (e).
5. US Dept of Defense. Occupational Medical Surveillance Manual. May 1998.
Publication No. DOD 6055.5-M. Available at: hnp:/Iwww.osha-slc.gov/SLTC/
medicalsurveillance. Accessed Feb 8,
2000.
6. US Dept of Health and Human Services, Public Health Service, Centers
for Disease Control, National Institutes
of Occupational Safety and Health.
NIOSH Criteria Documents Plus. (CDROM; Publication No. PB.) 1997;97:
502-582.
7. US Code of Federal Regulations. Federal
Old Age, Survivors, and Disability Insurance, Determining Disability and Blindness, Listing of Impairments. 1985. Title
20, Part 404, Subpart P, App. 1.
8. US Code of Federal Regulations. Federal
Coal Mine Health and SafetyAct of 1969,
as Amended, Part 7I8-Standards for
Determining Coal Miners' Total Disability or Death due to Pneumoconiosis.
1983. Title 20, Part 718.103.
9. American Medical Association. Guides
to the Evaluation of Permanent Impairment. 4th ed. Chicago: American Medical
Association; 1993.
10. American Thoracic Society. Evaluation
of ImpairmentlDisability Secondary to
Respiratory Disorders. Am Rev Respir
Dis. 1986;133:1205-1209.
11. American Thoracic Society. Single-breath
carbon monoxide diffusing capacity (transfer factor): recommendations for a standard
teehnique-1995 update. Am J Respir Crit
Care Med. 1995;152:285-298.
12. Morris AH, Kanner RE, Crapo RO,
Gardner RM. Clinical Pulmonary Function Testing: A Manual of Uniform Laboratory Testing Procedures. 2nd ed, Salt
Lake City, UT: Intermountain Thoracic
Society; 1984.
13. Wasserman K et al. Principles of Exercise Testing and Interpretation. 2nd ed.
Philadelphia: Lea & Febiger; 1994.
14. American Thoracic Society. Guidelines
for methacholine and exercise challenge
testing-1999. Am J Respir Crit Care
Med. 2000;161:309-329.
15. Graham WG, O'Grady RV, Dubuc B.
Pulmonary function loss in Vermont
granite workers. A long-term follow-up
and critical reappraisal. Am Rev Respir
Dis. 1981;123:25-28.
16. Townsend Me. The effects of leaks in
spirometers on measurements of pulmonary function: the implications for epidemiologic studies. J Occup Med. 1984;26:
835-841.
17. Townsend MC, Morgan J, Durkin D,
DuChene AG, Lamb S. Quality control
aspectsof pulmonary function testing in the
Multiple Risk Factor Intervention Trial.
ControlClin Trials. 1986;7:179S-192S.
18. Townsend MC. Standardized PFTs in the
occupational setting, Parts I and II.
NAOHP Clin Care Update. 1998;4:1920.
19. Scanlon PD, Hankinson J. Physiologic
methods. In: Harber P, Schenker MB,
Balmes JR, eds. Occupational and Environmental Respiratory Disease. St Louis,
MO: Mosby; 1996:39-54.
20. Gardner RM, Chairman. ATS statement-Snowbird workshop on standardization of spirometry. Am Rev Respir Dis.
1979;119:831-838.
21. American Thoracic Society. Standardization of spirometry-1987 update. Am Rev
Respir Dis. 1987;136:1285-1298.
22. American Thoracic Society. Standardization of spirometry: 1994 update. Am J
Respir Crit Care Med. 1995;152:11071136.
23. American Thoracic Society. Lung function testing: selection of reference values
and interpretative strategies. Am Rev Respir Dis. 1991;144:1202-1218.
24. Hiebert T, Miles J, Okeson GC. Contaminated aerosol recovery from pulmonary
function testing equipment. Am J Respir
Crit Care Med. 1999;159:610-612.
25. Kendrick AH, Smith EC, Leeming JP.
Bacterial colonization as a potential
source of nosocomial respiratory infec-
26.
27.
28.
29.
30.
31.
33.
34.
35.
36.
37.
38.
39.
40.
41.
tions in spirometers. Eur Respir J. 1997;
10:1694-1695.
Leeming JP, Pryce-Roberts DM, Kendrick AH, et al. The efficacy of filters
used in respiratory function apparatus. J
Hosp Infect. 1995;31:205-210.
RutaIa DR, Rutala WA, Weber DJ, et al.
Infection risks associated with spirometry. Infect Control Hosp Epidemiol. 1991;
12:89-92.
US Code of Federal Regulations. Cotton
Dust. Rev 1985. Title 29, Part 1910.1043
(h) and Appendix D.
Horvath EP Jr, ed. Manual ofSpirometry
in Occupational Medicine. Atlanta, GA:
Centers for Disease Control, National
Institute for Occupational Safety and
Health; 1981.
Enright PL, Hyatt RE. Office Spirometry.
Philadelphia: Lea & Febiger; 1987.
Hankinson JL. Instrumentation for spirometry. State of Art Rev Occup Med.
1993; 8:397-407.
32 Ruppel GL. Manual of Pulmonary
Function Testing. 7tlI ed. St. Louis:
Mosby; 1998.
Hankinson JL. Beyond tlIe peak flow
meter: newer technologies for determining and documenting changes in
lung function in the workplace. State of
Art Rev Occup Med. 2000;15(2). In
press.
Hankinson JL, Gardner RM. Standard
waveforms for spirometer testing. Am
Rev Respir Dis. 1982;126:362-364.
Nelson SB, Gardner RM, Crapo RO, et
al. Performance evaluation of contemporary spirometers. Chest. 1990;97:288297.
Hankinson JL, Wagner GR. Medical
screening using periodic spirometry for
detection of chronic lung disease. State of
Art Rev Occup Med. 1993;8:353-361.
Enright PE, Johnson LR, Connett JE,
Voelker H, Buist AS. Spirometry in the
lung health study. 1. Methods and quality
control. Am Rev Respir Dis. 1991;143:
1215-1223.
Hankinson JL, Bang KM. Acceptability
and reproducibility criteria of the American Thoracic Society as observed in a
sample of the general population. Am Rev
Respir Dis. 1991;143:516-521.
Enright PL. Surveillance for lung disease: quality assurance using computers
and a team approach. State of Art Rev
Occup Med. 1992;7:209-225.
US Code of Federal Regulations. Access
to Employee Exposure and Medical
Records. 1988. Title 29, Part 1910.1020.
The National Lung Health Education
Program Executive Committee. Strategies in preserving lung health and preventing COPD and associated diseases:
244
the National Lung Health Education Program (NLHEP). Chest. 1998;113:123S-
155S.
42. Hankinson JL, Castellan RM, Kinsley
KB, Keimig 00. Effect of spirometer
temperature on measurement of FEV 1
shift changes. J Occup Med. 1986;28:
1222-1225
43. National Institute of Occupational Safety
and Health, Division of Respiratory Disease Studies. NIOSH Spirometry Training Guide. Bethesda, MD: NlOSH; 1997.
44. Kellie SE, Attfield MD, Hankinson JL,
Castellan RM. The ATS spirometry variability criteria: associations with morbidity and mortality in an occupationally
exposed cohort of coal miners. Am J
Epidemiol. 1987;125:437-444.
45. Eisen EA. Standardizing spirometry:
problems and prospects. State of Art Rev
Occup Med. 1987;2:213-226.
46. Pennock BE, Rogers RM, McCaffree
DR. Changes in measured spirometric
indices-what is significant? Chest.
1981;80:97.
47. US Code of Federal Regulations. Asbestos. Rev 1994. Title 29, Part 1910.1001
(1).
48. US Code of Federal Regulations. Benzene. 1987.Title 29, Part 1910.1028 (i).
49. American College of Occupational and
Environmental Medicine. Spirometry
in the occupational setting. Notes for
guidance. J Occup Med. 1992;34:559561.
50. American Association of Occupational
Health Nurses. Guidelines for Implemen-
tation of a Respiratory Surveillance Program. Atlanta, GA: AAOHN; Oct 1989.
51. Morris JF, Koski A, Johnson L. Spiro-
52.
53.
54.
55.
metric standards for healthy nonsmoking
adults. Am Rev Respir Dis. 1971;103:5767.
Crapo RO, Morris AH, Gardner RM.
Reference spirometric values using techniques and equipment that meet ATS
recommendations. Am Rev Respir Dis.
1981;123:659-664.
Knudson RJ, Lebowitz MD, Holberg CJ,
et al. Changes in the normal maximal
expiratory flow-volume curve with
growth and aging. Am Rev Respir Dis.
1983;127:725-734.
Ghio AJ, Crapo RO, Elliott CG. Reference equations used to predict pulmonary
function at institutions with respiratory
disease training programs in the United
States and Canada: a survey. Chest. 1990;
63:136-145.
Knudson RJ, Slatin RC, Lebowitz MD, et
al. The maximal expiratory flow-volume
curve: normal standards, variability, and
effects of age. Am Rev Respir Dis. 1976;
113:587-600.
Spirometry • Occupational and Environmental Lung Disorder Committee
56. Hankinson JL, Odencrantz JR, Fedan
KB. Spirometric reference values from a
sample of the general US population.
Am J Respir Crit Care Med. 1999;159:
179-187.
57. Hankinson JL, Kinsley KB, Wagner GR.
Comparison of spirometric reference values for Caucasian and African American
blue-collar workers. J Occup Environ
Med. 38:137-143, 1996.
58. Glindmeyer HW, Lefante n, McCollester
C, et al. Blue-collar normative spirometric values for Caucasian and AfricanAmerican men and women aged 18 to 65.
Am J Respir Crit Care Med. 1995;151:
412-422.
59. Coultas DB, Gong H, Grad R, et al. State
of the art: respiratory diseases in minorities of the United States. Am J Respir
Crit Care Med. 1993;149:S93-S131.
60. Hankinson JL. Pulmonary function testing in the screening of workers: guidelines for instrumentation, performance,
and interpretation. J Occup Med. 1986;
28:1081-1092.
61. Berry G. Longitudinal observations.
Their usefulness and limitations with special reference to the forced expiratory
volume. Bull Physiopathol Respir (Nancy). 1974;10:643-656.
62. Burrows B, Lebowitz MD, Camilli AE,
Knudson RJ. Longitudinal changes in
forced expiratory volume in one second
in adults. Methodologic considerations
and findings in healthy nonsmokers. Am
Rev Respir Dis. 1986;133:974-980.
63. Clement J, Van de Woestijne KP. Rapidly decreasing forced expiratory volume in one second or vital capacity and
development of chronic airflow obstruction. Am Rev Respir Dis. 1982;
125:553-558.
64. Vollmer WM. Reconciling cross-sectional with longitudinal observations on
annual decline. State of Art Rev Occup
Med. 1993;8:339-351.
65. Buist AS, Vollmer WM. The use of lung
function tests in identifying factors that
affect lung growth and aging. Stat Med.
1988;7:11-18.
66. Camilli AB, Burrows B, Knudson RJ, et
al. Longitudinal changes in forced expiratory volume in one second in adults. Effects
of smoking and smoking cessation. Am Rev
Respir Dis. 1987;135:794-799.
67. US Dept of Health and Human Services,
Public Health Service, Centers for Disease Control, National Institutes of
Health. Criteria for a Recommended
Standard: Occupational Exposure to Respirable Coal Mine Dust. Bethesda, MD:
USDHHS; 1995.
68. Tager m, Segal MR, Speizer FE, Weiss
ST. The natural history of forced expiratory volumes: effect of cigarette smoking
and respiratory symptoms. Am Rev Respir Dis. 1988;138:837-849.
69. Ware JR, Dockery DW, Louis TA, et al.
Longitudinal and cross-sectional estimates of pulmonary function decline in
never-smoking adults. Am J Epidemiol.
1009; 132:685-700.
70. National Fire Protection Association.
Medical Requirements for Fire Fighters,
NFPA 1582. 1997 ed. Quincy, MA: National Fire Protection Association; 1997.
71. American Thoracic Society. Guidelines
for the evaluation of impairment/disability in patients with asthma. Am Rev Respir Dis. 1993;147:1056-1061.
72. US Dept of Health and Human Services,
Public Health Service, National Institutes
of Health, National Heart, Lung, and
Blood Institute. National Asthma Educa-
tion and Prevention Program (NAEPP)
Expert Panel Report 2: Guidelinesfor the
Diagnosis and Management of Asthma,
Clinical Practice Guidelines. Bethesda,
MD: USDHHS; 1997. NlH Publication
No. 97-4051.
73. US Dept of Health and Human Services,
Public Health Service, National Institutes
of Health, National Heart, Lung, and
Blood Institute. Global Initiative for
Asthma: Global Strategy for Asthma
Management and Prevention: NHLB1/
WHO Workshop Report. Bethesda, MD:
USDHHS; 1995. NIH Publication No.
95-3659.
74. Buist AS, Connett JE, Miller RD, et al.
Chronic obstructive pulmonary disease
early intervention trial (lung health
study): baseline characteristics of randomized participants. Chest. 1993;103:
1863-1872.
75. Ghio AJ, Castellan RM, Kinsley KB,
Hankinson JL. Changes in forced expiratory volume in one second and peak expiratory flow rate across a work shift among
unexposed blue collar workers. Am Rev
Respir Dis. 1991;143:1231-1234.
76. Burge PS. Use of serial measurements of
peak flow in the diagnosis of occupational asthma. State of Art Rev Occup
Med. 1993;8:279-294.
77. American College of Chest Physicians.
Consensus statement: assessment of
asthma in the workplace. Chest. 1995;
108:1084-1117.
78. Gannon PFG, Burge PS. Serial peak expiratory flow measurement in the diagnosis of occupational asthma. Eur Respir J.
1997; 10(suppl):57s-63s.
79. Moscato G, Godnic-Cvar J, Maestrelli P,
Malo JL, Burge PS, Coifman R. Statement on self-monitoring of peak expira-
JOEM • Volume 42, Number 3, March 2000
tory flows in the investigation of occupational asthma. Subcommittee on
Occupational Allergy of the European
Academy of Allergology and Clinical
Immunology. American Academy of Allergy and Clinical Immunology. European Respiratory Society. American College of Allergy, Asthma and
Immunology. Eur Respir J. 1995;8:
1605-1610.
80. European Academy of Allergology and
Clinical Immunology Subcommittee on
"Occupational Allergy." Guidelines for
the diagnosis of occupational asthma.
Clin Exp Allergy. 1992;22:103-108.
81. Quackenboss JJ, Lebowitz MJ, Krzyzanowski M. The nonna1 range of diurnal
changes in peak expiratory flow rates.
Am Rev Respir Dis. 1991;143:323-330.
82. Enright PL, Lebowitz MD, Cockroft
DW. Physiologic measures: pulmonary
function tests. Asthma outcome. Am J
Respir Crit Care Med. 1994;149:S9S18.
83. Bernstein 01. Clinical assessment and
management of occupational asthma. In:
Bemstein IL, Chang-Yeung M, Malo J-L,
et al, eds. Asthma in the Workplace. New
York: Marcel Dekker; 1993:103-123.
84. Smith AB, Castellan RM, Lewis D, et al.
245
Guidelines for the epidemiologic assessment of occupational asthma. Report
of the Subcommittee on the Epidemiologic
Assessment of Occupational Asthma, Occupational Lung Disease Committee. J Allergy Clin Immunol. 1989;84:794-805.
85. Burge PS. Physiologic assessment of occupational asthma. In: Bernstein IL,
Chang-Yeung M, Malo J-L, et a1, eds.
Asthma in the Workplace. New York:
Marcel Dekker; 1993.
86. Hankinson JL, Das MK. Frequency response of portable PEP meters. Am J
Respir Crit Care Med. 1995;152:702706.